Area Forecast Discussion
Issued by NWS La Crosse, WI

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159
FXUS63 KARX 232328
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
628 PM CDT MON MAY 23 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 355 PM CDT Mon May 23 2016

At 3 PM, the upper level ridge and 1017 mb surface high, which
brought the dry weather to the region through the weekend, had
moved east into Michigan. Even though this was the case, southeast
winds in its wake have lowered dew points into the 40s in western
Wisconsin this afternoon. Meanwhile in northeast Iowa and
southeast Minnesota, southerly winds ahead of a long wave trough
have allowed surface dew points to climb into the 50s and lower
60s. Scattered showers and storms have developed west of a Lake
City MN to Charles City IA line. These are developing ahead of a
short wave trough moving northeast out of north-central Iowa and
in the right entrance region of a 90-knot 250 mb jet.

For tonight, the 23.12z models are in fairly good agreement that
the short wave in Iowa will move northeast through eastern
Minnesota and northwest Wisconsin. Meanwhile another short wave
trough will move to the south of the region. Many of the meso
models are too rambunctious with their reflectivity products for
tonight. This is due to these models being too high with their dew
points and this ultimately causes their CAPES to be too high.
Overall prefer the HRRR and RAP solutions the best. They are still
a bit too high with their dew points, but their reflectivity looks
the most realistic. Due to this, kept the highest rain chance
north of Interstate 90.

On Tuesday, the models continue to show that a weak trough will
settle south across the Upper Mississippi River Valley. There is
very little convergence along this trough. With diurnal heating,
the 0-1 km mixed layer CAPES climb into the 1500 to 2500 J/kg
ahead of this system. Any convection that does happen to develop
will likely have to rely any residual boundaries left over from
tonight and differential heating during the afternoon. Due to
this, kept rain chances in the 20 to 40 percent range. With
continual weak 0-3 km and 0-6 km shear, no organized severe
weather is anticipated.

.LONG TERM...(Tuesday night through Monday)
Issued at 355 PM CDT Mon May 23 2016

From Wednesday night into Sunday, the models are showing a wide
variety of solutions, so confidence remains low on any timing of
precipitation and whether there will any organized severe weather
will even occur.

The ECMWF moves a trough through the Upper Mississippi River
Valley on Wednesday night and has the surface warm front well to
our south of Thursday. Some elevated instability (1-2 K 0-1 km
mixed layer CAPES) moves into areas south of Interstate 90 late
Thursday afternoon and evening, but there is only weak shear
across the area. With the front remaining to our south, the
instability remains less than 1000 J/kg through Saturday night and
then moves north on Sunday as a short wave ejects out of the
western trough. However this signal has been really inconsistent.

Meanwhile the NAM keeps the cold front west of the area on
Wednesday night. This allows the 0-1 km mixed layer CAPES to climb
into the 2 to 4K J/kg range on Thursday afternoon. While there is
sufficient deep shear for supercell development, there is a cap
aloft between 825 and 775 mb which may prohibit convective
development.

The GFS shows similar instability on Thursday afternoon. However
it has marginal shear. For the remainder of this period, both the
instability and shear remain weak.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 628 PM CDT Mon May 23 2016

Primary concern is watching thunderstorms this evening, mainly
impacting KRST as environment is less favorable at KLSE. Ceilings/
visibility may briefly drop into the MVFR range with stronger
storms, otherwise expect VFR conditions as storms move through the
region. Thunderstorm threat should diminish after 24.03Z with
scattered showers possible overnight.

Forecast guidance continues to hint at some MVFR ceilings
developing at both TAF airfields in the 24.10Z to 24.12Z time
frame. Will keep this idea from previous forecast with improving
conditions back to VFR by late Tuesday morning. Strong south-
southwest winds, gusting at times above 30 kts will subside this
evening, becoming light overnight and then slowly turn to the
west-northwest late in the period.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...ROGERS



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